


Baby I'm preying on you

by reetsu



Category: Voltron: Legendary Defender
Genre: Alpha!Shiro, M/M, Omega!Keith, alpha!kuro, mermaid au, non-consensual use of pheromones
Language: English
Status: In-Progress
Published: 2017-08-04
Updated: 2017-09-26
Packaged: 2018-12-11 03:11:01
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 4
Words: 6,625
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11705586
Author URL: https://archiveofourown.org/users/reetsu/pseuds/reetsu
Summary: “Why are you doing this?”“Because Shiro loves you. That’s why I’m going to ruin you for him.”[mermaid au where Kuro does something very terrible to Keith]





	1. Chapter 1

_‘Aaaaw, aren’t they so adorable. Makes me want to throw up.’_ It’s what Kuro thinks as he spies on his brother and his mate during one of their romantic moments.  
Shiro peppers kisses all over Keith’s face, who blushes at how sappy his alpha is being in that moment.  
Shiro had to leave to take care of something that princess Allura had requested of him. Apparently dead merman had been found and Allura suspects that there is a killer on the loose, so she asked Shiro to go take a look at the area. He asks Keith to be careful while swimming around. The two hug and part ways.  
Kuro follows Keith, keeping a safe distance between the two to avoid being noticed.  
He and his twin brother Shiro never had a good relationship. Since they were kids, things had been complicated between them. Kuro always believed that his brother hated him.  
Things got worse when Shiro found out that Kuro had joined the Galra empire and was working with them in secret to take down King Alfor.  
Shiro found out that Kuro was betraying his kingdom. He gave Kuro one last chance to redeem himself.  
The two fought. Shiro was the one who lost an arm, but Kuro was the one who lost the fight. Kuro was also the one who gave Shiro the scar he has on his face.  
Shiro left him there bleeding. He couldn’t bring himself to kill Kuro and instead warn him to never come back to the kingdom or else next time he wouldn’t hesitate to put an end to his life. Haggar found him and brought him to Zarkon’s castle to heal him. The witch’s magic turned his eyes into a bright yellow.  
It had been nearly two years since then.  
King Alfor congratulated Shiro by making him the chief of the royal guard. Kuro thought Shiro was going to take advantage of being on the King’s good graces to ask Princess Allura to be his mate, like many would love to. He, instead, chose this little omega named Keith.  
Kuro was the one who killed those merman. They spotted him sneaking into the kingdom and he had to shut them up or his presence would be revealed too soon.  
Keith went scavenging into some place far away from the kingdom, ignoring Shiro’s advice to stay safe.  
Keith swam down into a crack where hardly any light shines down on it, hoping to find treasures there. There was nobody else around and Keith had swam into a place where Kuro could easily cornered him.

Keith was the perfect prey for Kuro.

Keith quickly became aware of Kuro. He dropped the shiny rock he was holding and turned around. His face dropped when he saw how Kuro was an exact copy of Shiro, except for the yellow eyes.  
“Who are you?” Keith adopted a defensive stance, raising his fists.  
_‘So Shiro didn’t tell you anything about me.’_  
Kuro swam closer until he was just inches away from Keith. The omega didn’t have any time to do anything as Kuro lunged at him and grabbed his wrists, pinning him against the rock wall behind him.  
"I'm Kuro. Nice to meet you." he flashed him a wolfish smile.  
Shiro had been blessed with good looks, that's what their mother had always said. Shiro could have had the prettiest omegas, females or males, as his mate and they would feel lucky to be.  
But instead he chose such a plain looking one like Keith.  
Despite the appealing red color of his scales and having a lithe body, there wasn’t anything special about him. And yet, Shiro cherished him so much and picked him as his lover for life.  
Kuro took a closer inspection on Keith, searching for any love bites or hickeys that Shiro could have left on him, only to see that the omega’s skin didn’t have any flaw on it, aside from a few tiny white scars on his arms that he must have gotten during a fight or a scavenging adventure.  
He also noticed that there was barely any of Shiro’s scent lingering on Keith.  
Every alpha knows that the best way to keep unwanted competition away from their mate is to mark them down as their own.  
It was his brother’s fault that any alpha could easily snatch Keith away.  
Keith finally pulled his arm free from Kuro’s grip and swung it back, punching Kuro in the jaw.  
Kuro let go of his other arm and Keith took that opportunity to swim up the fastest he could. Kuro rubbed his face and could taste blood in his mouth.  
_‘Damn, this little omega does know how to pack a punch.’_  
Kuro wasted no time chasing after him. Keith looked over his shoulder, panicking at how quickly Kuro had managed to catch up to him, but he refused to get caught again. He resorted to smack Kuro on the head with his tail, which disoriented Kuro for a few seconds.  
Keith was sure he could escape from him as long as he kept swimming. He knew his way around this area and could find a path that would lead him back to safety.  
Strong arms wrapped around him from behind, restraining him. Keith thrashed around, but Kuro wasn’t going to let him get away again.  
“I think I now have an idea why Shiro likes you so much.” Kuro swam down, back into the darkness, pulling Keith with him.  
“Come on, don't struggle. It will feel good if you let it.” Kuro gave Keith’s ear a playful bite, causing Keith to go into a hysterical fit.  
Keith was turned around so he was facing Kuro, who pressed his large body against him, slamming Keith’s back on the rock wall. Keith’s clawed Kuro’s shoulders, trying to push him away. Kuro’s lips formed into a little smirk, amused by Keith’s attempts to stop him from going with this.  
Kuro leaned into him and started trailing kisses up Keith’s neck. Keith cringes away, but Kuro grabs his hair and tugs it harshly, forcing Keith to tilt his head up. Kuro takes advantage of Keith letting out a small gasp of pain to slide his tongue inside of his mouth. Kuro looks into Keith’s eyes, loving the mix of emotions he sees in them: anger, fear, disgusts.  
Keith bites down on Kuro’s tongue, which makes Kuro break their kiss.  
The little one wasn’t going to submit so easily. Kuro wondered if Keith had made Shiro chase after him or if he quickly accepted the alpha.  
There was one thing he could do to make Keith more compliant.  
Kuro released his pheromones. No omega could resist the effects an alpha’s scent had on their bodies. And similar to Shiro, Kuro’s pheromones were strong and could make anyone submit to them.  
The way Keith’s expression softens and the blush that appears on his face prove that it was having an effect on him.  
Keith stopped his struggle and Kuro was no longer holding him down.  
Kuro licked his lips, loving the image of the omega in front of him; submissive and begging to be touched.  
He pressed the palm of his hand on Keith’s chest and slowly move it down all the way to his navel. Keith’s arched his back, leaning into his touch.  
Kuro’s lips were on Keith’s neck again, sucking on Keith's porcelain skin until it bruised. Kuro loved the moans that he was getting out of Keith as well as the scream that came out of his mouth when he sank his teeth into Keith’s shoulder. The once unmarked omega now had hickeys and bruises all over his body.  
Kuro’s fingers dig into the flesh of Keith’s hips, with enough strength to bruise. Kuro imagined how Shiro’s reaction would be when he found Keith once he was done playing with him. He would be mad, furious. He probably would set on a search for Kuro, wanting to find him and kill him.  
Kuro was tired of foreplay and decided to finally have some real fun.  
He found Keith’s slit and slid his fingers inside of it. Keith tried to shove his hand away, but he was too weak to do so. Kuro moved his fingers inside, feeling how Keith’s entrance had self-lubricated as a response to his pheromones. Keith was a panting mess, begging for Kuro to stop.  
“Why are you doing this?”  
Kuro was impressed that Keith could still talk properly with how overstimulated he was.  
“Because Shiro loves you. That’s why I’m going to ruin you for him.”  
Kuro felt like Keith was ready to take him. His penis slid out of his slit and pressed against Keith.  
“No!”  
Keith screamed as Kuro began to enter him. He started slow, but then he slammed his full length inside in one thrust.  
He didn’t wait for Keith to accommodate to his width before beginning to move his hips back and forth. Keith was crying at the pain of being torn open. The worst part is that his body was still affected by Kuro’s pheromones so his hips moved along with the thrusts.  
Kuro could tell Keith’s climax was close. His nails dragged across the skin of Kuro’s back, scratching him.  
He gave a small peck on Keith’s cheekbone, the only sign of gentleness he had shown until now.  
Kuro made sure his scent clung onto Keith so that Shiro and every alpha could smell it and know that someone had already claimed him.  
He kissed him as he gave one final thrust, releasing his load inside of him. Keith’s orgasm was muffled by their kiss.  
Kuro finally backed away, giving Keith some space. Keith sank down until he was sitting in the sand. His tail wrapped around him protectively and he hugged himself.  
He sobs, keeping his head down.  
Kuro admires his work.  
He moves closer and whispers to Keith’s ear “When Shiro asks who did this to you, tell him it was me. Don’t forget to say my name.”  
Kuro swims away, leaving Keith alone.

Lance and Hunk happened to be swimming by. Hunk was rolling his eyes as Lance was telling one of his tales about how he had conquered the heart of a beautiful female omega. The sound of Keith crying reached Hunk’s ear, making him stop in his tracks.  
Hunk hesitated a little in diving down into the darkness, afraid of what dangers could be hiding there, but he couldn’t ignore the fact that someone down there was in need of help. Lance followed behind him.  
They weren’t expecting to find Keith curled up on himself.  
“Keith...” Hunk carefully approached him.  
Both Hunk and Lance gasped as they saw all the bruises on Keith’s body as well as the bite mark on his shoulder that would definitely leave a scar.  
The strong scent that they could smell from Keith’s body could only belong to an alpha.  
Lance and Hunk felt their stomach drop as realization of what had happened hit them.  
“Go find Shiro. I will take Keith to the castle.”  
Lance needed a few seconds to recompose himself before swimming away in search for Shiro.  
Hunk tried to scoop Keith into his arms. Keith screamed and pushed him away.  
“Keith, it’s okay. It’s me, Hunk.” he did his best to calm him down.  
Keith finally let himself be carried by Hunk. He wrapped his arms around Hunk’s neck, burying his face on his shoulder as he continued to whimper.  
As he took him to the castle, Hunk hummed a soothing song, which helped to calm Keith down a little.

\-----

Lance had a hard time keeping up with Shiro.  
Once he told him what had happened, Shiro dashed towards the castle at high speed. They swam past the gates and found Coran and Allura, both with expressions of distress on their faces.  
“Where’s Keith?”  
Allura leads him to the room where Keith was.  
Coran gave Keith a little bit of medicine to help ease his pain, but besides that there was nothing else they could do for him.  
Keith was lying down in a bed in the middle of the room. The only ones with him were Hunk and Pidge, who were keeping an eye on him. Keith was staring blankly into one of the walls of the room, his eyes puffy and red from all the crying. When he felt Shiro’s presence, his eyes fell on him. Keith stretched his arms and Shiro hurried to hug him.  
Keith clung on to him, resting his head against Shiro’s neck. Shiro could feel Keith shaking.  
Pidge and Hunk left, believing that the two lovers would prefer to be alone.  
Shiro kept his arm wrapped around Keith's waist.  
Shiro was horrified by the damage that Keith’s attacker had done to his body. There were hand prints shaped bruises on Keith’s wrists, meaning that the attacker had held or pinned him down. Keith must have been so scared and helpless.  
Shiro couldn’t ignore the scent that was coming from Keith. The scent of another alpha. It seemed familiar but Shiro couldn’t remember from who.  
“Keith.” Shiro’s hand gently caressed his cheek “Who did this to you?”  
Whoever this monster was, Shiro was going to find him and make him pay for what he did.  
“He looked exactly like you.”  
Shiro’s whole body tensed  
_‘Could it be? Please no...’_  
“Kuro. It was the name of the one who did this to me.”  
Shiro’s heart was racing. Anger was boiling inside of him. He clenched his fist until his knuckles turned white.  
_'Kuro...'_  
Shiro bumped his forehead with Keith’s.  
“I’m so sorry, Keith.”  
Shiro was going to find him even if he had to swim through the seven seas. He will not show any mercy once he kills him for hurting Keith.


	2. Chapter 2

**Notes for the Chapter:**

> At the time, when I posted the first chapter, I was still waiting for someone to put season 3 online so I had no idea Kuron was going to become an actual character.
> 
> So to make things clear. This Kuro is NOT Kuron.

One week had passed.

Shiro had to refrain from physical affection until he was sure Keith was completely comfortable with it. Hugs were fine, but Shiro had to be careful. Keith’s skin, where Kuro had bruised him, was still sensible and just Shiro’s fingers accidentally brushing over it made Keith flinch.

Keith was okay with cuddling with Shiro in their bed when they slept. It made him feel safe. Shiro didn’t push past Keith’s boundaries. He kept an arm draped over the omega, but didn’t kiss him, like he usually did as his way of saying ‘good night’.

Keith has started to have nightmares since the attack. He screams and struggles as if something or someone was holding him down.

One night, Shiro tried to calm him down, but when Keith opened his eyes and saw Shiro’s face, he slapped the alpha across the face. Keith realized what he had done and wrapped his arms around Shiro’s neck, hugging him.

“I’m sorry. I thought you were him.”

\----

Shiro spent his days searching for Kuro, while Keith and the others kept guard in the castle. Allura and Coran advised Keith to rest for a while, but Keith refused to sit around and do nothing. Shiro asked Lance and Hunk to keep an eye on him while he was away. 

Pidge and Matt took care of improving the castle defenses. King Alfor and Allura had to reassure the citizens of their kingdom that although someone like Kuro was on the loose, they were doing the best they could to capture him before he hurt another innocent soul.

Shiro swam around the kingdom, keeping his eyes open to catch any glimpse of Kuro.  
“Shiro!”

He stopped when he heard Allura call for him. She was standing by his side now.

“Princess.”

“I will help you search.”

Shiro nodded. Allura was a fast swimmer like him, so she could easily keep up with him.

“There something I need to talk with you.” Allura started “It’s about Keith.”

Shiro didn’t look at her, keeping his attention on their surroundings.

“I assume you have talked about what happened. Still, I believe there are some things Keith wants to tell you, but he can’t bring himself to.”

Shiro finally turned his head to look at her.

“What do you mean?”

Allura bit her bottom lip and tucked a lock of her hair behind her ear.

“I overheard a conversation between Coran and Keith. When Coran was removing Kuro’s scent from him.”

Coran had applied some sort of ointment that removed an alpha scent from one’s skin. The other night, Keith confessed that he could still smell it on him.

“Keith shared with Coran that he was afraid he was no longer suited to be your mate, after what happened. Well, he didn’t say it like that. He just implied that that was what was bothering him.”

“What did Coran said?”

“Coran told him that there was no doubt that you loved him and you still do. But you know Keith.”

Shiro didn’t want to force Keith to talk unless he wanted to, but maybe he could gently coax Keith to share the doubts that were plaguing him.  
Allura could see that Shiro was thinking about it, so she remained silent as they continue to swim.

\----

Keith, despite Hunk’s insistence, skipped dinner and decided to go to his room. He rested on his bed, rolling to the side that Shiro slept in when he kept him company at night. His scent lingered on it. Keith breathed it in. 

His fingers lazily brushed over the scar of the bite left by Kuro. Coran couldn’t do anything about it, so Keith had to learn to live with it. Keith hated the way Shiro looked at it. He could see the guilt and anger in his eyes. Guilt for not being able to do anything to save Keith at that time and anger that he felt for Kuro.

Shiro was going to find a better mate. A better mate than Keith ever was. Even before any of this happened, Keith had thought of himself as not being good enough for Shiro. In the emotional state he was in, Keith couldn’t give Shiro everything he wanted, even if he tried. 

Keith was snapped of his thought by the door of his room opening. It was Shiro and he had a worried look on his face.

“Hunk told me you didn’t eat.” 

“I didn’t feel like it.”

“I can go fetch something for you to take a bite out of.”

“I’m not hungry.”

Shiro swam close to him, sitting down on his bed. 

“Keith. Is there something troubling you?”

Keith cast down his eyes.  
“No, nothing.”

He didn’t want to talk about this with Shiro. He decided to try to avoid this conversation. His hands found their way to Shiro’s shoulders and he moved to kiss him. It was a messy kiss and Shiro wasn’t even returning it. Keith wanted to prove he could still be a good omega to Shiro, then maybe Shiro wouldn’t want to replace him. He leaned back in his bed, pulling Shiro along. He grabbed Shiro’s wrist and lead his hand down to where his slit was. He was shaking and he knew Shiro had noticed it. If Shiro released his pheromones, things would go so much easier.

“Keith.” Shiro freed his hand from Keith’s grasp. He looked at Keith with concern. 

“Please, just let me do this for you.” Keith’s voice cracked, “If I can’t even do this for you, then what good am I for?”  
Keith hide his face behind his hands as he began to cry uncontrollably. Shiro hated him, for sure. What alpha would like to have an omega like Keith as theirmate? An omega who can’t stand being touched by their lover.

_‘Because Shiro loves you. That’s why I’m going to ruin you for him.’_

And he did. Kuro ruined him for Shiro and anyone else. 

“Keith.” Shiro gently pried his hands away from his face. Keith kept his eyes closed, not feeling capable to look at Shiro in that moment.

“You’re not something that I own, Keith. You’re the one I love with all my heart. And I will stay by your side, always. No matter what.”

Keith opened his eyes.  
Shiro loved him. And he loved Shiro. And they were going to get through this together.

\------

The next morning, Shiro woke up at dawn. Keith, still laying in bed and sleepy, took hold of his arm, not letting him leave.

“Stay.”

“Sorry, baby. King Alfor wants me to get the royal guard ready early in the morning.”

Keith pouted and Shiro pecked his cheek.

\------

Hunk was overjoyed to see Keith joining them for breakfast. Matt and Pidge, despite being busy discussing some new device they were working on, still stopped their conversation to say 'good morning' to Keith. Lance was the last one to arrive and he too was happy to see Keith there. 

They all could tell that Keith finally had the good night sleep he deserved, without any nightmares startling him awake.

\------

Keith decided to join Hunk and Lance on their errand. Coran requested them to get a few plants for him, since his medicine stock was starting to run low.

Matt and Pidge wanted to test the new defense mechanism they installed in the castle, so they told Keith it would be fine if he went along with them.

Keith was kind of nervous at the beginning. He hadn’t left the palace since the accident and his paranoia got the best of him, making him look over his shoulder constantly. He kept himself always close to the others. Hunk and Lance also made sure to look out for Keith.  
Lance and Hunk constantly goofing around helped lighten the mood. Keith still had the fear that Kuro would appear out of anywhere. He was afraid he was going to find those yellow eyes staring at him and he would be Kuro’s prey once more.

Keith’s jumped when Lance put a hand on his shoulder. 

“I’m sorry, Keith. I didn’t mean to scare you.”

“No, no... it’s fine.”

“We have the plants. We should head back to the castle.”

The three were swimming their way back when something caught his eye. Laying on the sand were two identical light pink seashells. An idea ran through Keith’s head. 

When Keith was putting the seashells in his satchel, he felt a shiver ran through his spine. He turned and looked around.

“What’s wrong?” Hunk asked.

“I just...” Keith rubbed the back of his head “I just felt like someone was watching. Probably nothing.”

Kuro poked his head from behind the rock he was hiding. He watched as the three merman swam away, unaware that he was right there.

He licked his lips. He wanted to hunt Keith down again once he had the chance, but he first had to finish his mission.

Then he could have some fun with the little omega.

\-----

Keith crafted the seashells into necklaces. He asked Shiro to close his eyes as he put the gift around his neck. 

“Now you can open them.”

Shiro looked at it and smiled.

“It’s beautiful.” 

His smile grew wider when he saw that Keith was also wearing a necklace with a seashell that looked exactly the same as his. 

“I decided to turn them into matching necklaces.” Keith blushed and looked away. “As a way for the others to be able to tell we are mates. And it can be the symbol of our union. I know it’s cheesy...”

Shiro leaned down and kissed the top of his head.

“I love you.”

“I love you too.”

**Notes for the Chapter:**

> I had the idea for the seashells because I went to the beach this morning and found one.
> 
> I'm going to be out for a week, in France, for a family vacation, so don't expect the next chapter to be out in a few days.
> 
> Please leave a comment if you're enjoying this story.


	3. Chapter 3

“And done!” Pidge finished adjusting the prosthetic she made especially for Shiro.

“Pidge, this is...”, he was ecstatic when he saw the metal fingers moving at his command, “... this is amazing!”

Pidge rubbed the back of her head, “I knew all that scrap that humans throw into the water could be used to create something good.”

Shiro continues to experiment the metal arm, picking up one of Pidge’s tools with it.

“Be careful, okay. It can still break if you overdo it.”, she reminded him.

He set down the tool on the table.

“Don’t worry, I will be. Thank you so much.”

There was a knock on the door.

“Come in.” Pidge gave permission.

Allura opened the door and got inside Pidge’s workshop, “I hope I’m not interrupting something.”

“Pidge here built me a new arm.”, Shiro showed off his prosthetic.

“Well done, Pidge.”, Allura was impressed. Pidge smiled brightly at the praise.

Allura's expression changed from amazed by Pidge’s work to serious as she looked at Shiro.

“Shiro, I would like to discuss something very important to you. It’s about Kuro.”, the mood in the room shifted abruptly. 

Pidge occupied herself with cleaning her work table, so she could give the two some privacy.

“Did they find him?”

“No.” 

Shiro sighed. That bastard was hiding somewhere and wasn’t making things easy for them.

“I was thinking about why would Kuro return, after this time.” Allura clasped her hands together, “I don’t think this is just him getting his revenge against you for what happened years ago.”

Shiro closed his eyes, his fingers moving to trace over the scars left in his skin where his arm had been cut off during the fight against his twin.

“I believe Kuro is still under Zarkon’s orders and he was sent to threaten the safety of our kingdom on his behalf.”, she swam close to him and put a hand on his shoulder, “Keith’s attack was definitely his way to get to you. To provoke you. He wanted you to know that he was back. And he used your mate for that.” Allura’s eyes were filled with sadness as she remembered the state Keith was in when Hunk brought him to the castle.

Keith had been a victim in all of this. He didn’t deserve any of what had happened to him.

“The fact that he is making it harder for us to find him, means he still has unfinished business here to take care of. And once he has fulfilled his mission, he will appear in front of you, knowing that you will want to make him suffer for what he did.”

Shiro pondered what Allura was theorizing.

If Kuro just came for a rematch, he would have given Shiro a way for him to track him down, instead of playing this game of hide and seek.

Then it hit Shiro.

“The celebration, tomorrow night...”  
Once a year, leaders of every kingdom in the seven seas, travelled to King Alfor’s kingdom to attend a party that was held in his castle.

“I already talked about it with my father.”, Allura pulled her hand away from Shiro’s shoulder, “It is the perfect opportunity for Kuro, and any other Zarkon’s soldiers that he might have helped sneak in secret, to attack. But we will have a way to deal with it if that happens.”, she smiled with confidence.

“Pidge and Matt improved the security of the castle. If something is to happen tomorrow, I trust it to ensure the safety of our guests.” Allura turned her head to Pidge, who gave a thumbs up as a response.

“Princess Allura...”

“We can’t let fear control us. If we choose not to host the party tomorrow, Kuro will know he managed to intimidate us. I want him to know that we are not afraid of him and we will fight him with everything we got.”

\----  
Shiro looked at himself in the mirror of his room. He ran a hand through his hair, trying to comb it. Arms encircled him from behind. Keith bumped his forehead against his back.

“You look great, don’t worry.”

Shiro turned around and hugged the omega. His metal arm rested against the small of Keith’s back and gently brushed the knuckles of his flesh hand along his lover's face.

He leaned down and kissed him.  
Keith was slowly becoming comfortable with affections again and no longer flinched. There were still some things that made Keith feel uneasy. Shiro was very respectful about it and avoided causing Keith any distress.

Both were wearing the sea shell necklaces, crafted by Keith, around their necks..

“Well, let's go then.”

\----  
Guests swam through the ballroom, enjoying the party. 

Despite being guests as well, Shiro and the others were paying close attention to any suspicious activity. 

Lance didn’t miss the opportunity to flirt with a few of the female attending the celebration. Hunk stayed close to him, eating one of the many delicious plates that had been prepared by their very skillful chefs for this night. Pidge and Matt were discussing about gadgets with some engineers from another kingdom. 

Shiro leaned against one of the walls, his arms crossed over his chest. He started to think about what the princess told him yesterday. If Kuro was to attack now, he and the others would have to act fast.

He started to think about how the events would unfold. 

Pidge and Matt would activate the barrier to make sure that Kuro or any other intruder couldn’t escape, and also making impossible for any enemy reinforcements to enter. From then on, Shiro, Lance and Hunk would fight against Kuro and any of his allies that he might have brought along.

Allura and Coran would take the guests to a safer place in the castle, away from their conflict.

Where would Keith be, though? Would he join the fight or would he help protect the guests? Would Shiro let Keith even be part of their attempt at taking Kuro down or would Shiro tell him to stand back?

Shiro was snapped of his thoughts when, from the corner of his eye, saw his mate swimming towards him.

Keith, unexpectedly, wrapped his arms around Shiro’s neck and and rested his cheek on his shoulder.

“What’s wrong, Keith?”

“I don’t like the way some alphas are eyeing me. This way at least they’ll know I have a mate.” a soft blush crept on Keith’s face, "And a few of the omegas have also been staring at you."

Shiro couldn’t resist smiling at how cute Keith was, and nuzzled his nose, which only made him redder. Keith responded to it by kissing the corner of Shiro’s mouth, making him blush in return. 

Alfor stood in the middle of the room, glass raised high as he began his speech. Allura was at his side, the vibrant pink scales of her tail and forearms shined brightly. 

King Alfor thanked the guests for their attendance and let them know that he appreciated their commitment to maintaining peace and union between the kingdoms. 

Keith leaned his back against Shiro’s chest as he listened to the king’s words. The alpha’s arms remained around him, and Shiro rested his chin on top of his head.

The omega suddenly felt a weird sensation. He felt like he was being watched. He looked to the side and what he saw made his blood run cold.

Two bright yellow eyes were staring at him. Even hidden in the shadows at the entrance of the ballroom, Keith could still make out the face of his attacker, who flashed him a malicious grin. 

“Keith?” Shiro noticed quickly that something was wrong.

Keith was hyperventilating and his body tensed up. 

Shiro turned to look at where Keith’s glance was fixated, but he only managed to catch a glimpse of a tail before it disappeared from his sight.

Black and white scales. Like him. Like Kuro.

Keith slipped out of Shiro’s hold, before Shiro could do anything to stop him

“Keith!” Shiro's yell interrupted Alfor’s speech, everyone's attention turning to him.

Keith swam out of the room, in the same direction that Kuro fled to.

Shiro glanced over his shoulder, his eyes focused on Allura, “He’s here!”

Allura knows what to do. 

Shiro followed after Keith, swimming as fast as he could, hoping he could catch up to his lover in time, before something bad happened.

Kuro’s smile grew wider as he now had the two chasing after him.

_‘We’re going to have some fun.’_

**Notes for the Chapter:**

> If you liked this work, please leave a comment, I will appreciate it very much.
> 
> Hope you like that little bit of Keith and Shiro at the party.
> 
> I also realized I never properly described how each of the characters look as mermaids. Their scales are the same color as their theme colors in the show and I realize how lazy of me was to, in the previous chapter, to never give a proper description.


	4. Chapter 4

**Notes for the Chapter:**

> Quick note. Things like barriers are possible under the sea because in this au the merpeople like Pidge and Matt can use magic for their inventions and to help protect the castle.

Shiro had lost Keith of his sight when his mate had turned a corner. Once Shiro reached that corner, in front of him was a long hallway with a stone archway at the end that lead to the outside. Keith had swam by here, chasing after Kuro. Shiro tried to stop him, not wanting Keith to go face him by himself, but Keith didn’t listen to him and continued to swim after the intruder.

The sight in front of him, once he swam past the archway, made his heart stop beating for a second, only for it to start beating frantically. 

Kuro was there. And so was Keith. 

His mate struggled to get free from the alpha holding him. Kuro had his arm wrapped around Keith’s neck, keeping him close to him. The barrier was activated and Kuro could not swim away from there.

Once Shiro’s presence was noticed, Kuro, who had whispered something into Keith’s ear, lifted his head and smiled devilishly at him.

“Shiro...”, Keith cried out. 

Kuro planted a kiss on Keith’s cheek, keeping eye contact with his twin as he did that. 

Shiro blood boiled with rage. Keith was serving both as a human shield and as a way for Kuro to provoke Shiro. 

Once he could get his hands on Kuro, he would beat and hurt him without any restrain. Make him suffer until he was begging Shiro to kill him to end his pain.

“Didn’t our mother used to tell us to share our toys, Shiro.”, a smirk spread on his face.

This wasn’t how Kuro had planned things to go. Even if he was excited to be able to prey on the little omega again, he only intended to do that once his mission was over. Then he could take care of his rematch with his brother. And then back to preying on the little omega. Kuro even had plans on keeping Keith to himself once he was done with his brother.

Kuro had been able to keep hidden from those who searched for him and neak into the castle during the party.

His task was to strike down king Alfor and princess Allura once he had the opportunity, until then he had to be in the shadows. A party full of guests wasn’t easy, but Kuro loved a challenge. Then he saw Keith and Shiro and couldn’t resist spying on their cute little moment, when Keith wrapped Shiro’s arms around himself.

The omega ended up finding him and Kuro had no choice but leave his hiding spot.

Like he had expected, Keith chased after him right away. Great. His stealth was ruined, but at least he got his brother’s mate to come after him all by himself.  
Kuro made his way outside and that was when the barrier was activated, making it impossible for anyone to enter or leave the area that was surrounded by it.

Well, damn it, Kuro wasn’t expecting that. 

And then Keith caught up to him. Kuro turned to look at him and found those pretty violet eyes glaring at him, filled with anger and wrath. But there was something else. Fear. Yes, Keith was terrified of him. Even if he clenched his hands into fists and held them high, he was trembling. 

Kuro didn’t move, letting Keith throw the first punch. And that was Keith’s mistake. Kuro dodged him and grabbed his arm, twisting it behind his back.

Keith tried to hit him with his tail and with his free arm, but was only making things worse for himself. An arm looped around his neck and pulled him closer, his back pressing against Kuro’s chest.

“Have you missed me?”, Kuro mocked. 

And that was when Shiro showed up.

Keith’s nails scratched Kuro’s arm, leaving red lines across his skin. He refused to give up easily, but Kuro’s grip on him didn’t get looser. 

The alpha decided to make things easier for himself.

Keith’s blood turned cold when the familiar scent invaded his nostrils. The scent of that dreadful day. Kuro was releasing his pheromones.

‘No, no, no, no, no!’

Shiro saw Keith’s eyes become half-lidded and his body going slack, his struggling coming to an end. He realized what was happening.

“Let go of him!”, Shiro roared.

His twin opened his mouth, proudly baring his sharp teeth. He moved his head down and let his canines slightly graze over the skin of Keith’s neck. The omega tilted his head to the side, presenting his neck to the alpha. A moan left his lips and Shiro could see a small blush on Keith’s cheeks.

Shiro knew he had to do something. He wanted to do something to stop this. But any wrong move and Keith could end up hurt. Although the situation he was in right now wasn’t any better.

Kuro’s hand gripped Keith’s chin and forced his head back. He held him in place as he kissed him roughly, his tongue forcing its way inside his mouth. There was no gentleness in his actions, only possessiveness. He wanted to claim Keith, not as a lover, but as his omega. 

A sob escaped from Keith’s throat when Kuro pulled away and bite into his bottom lip. The sound of it was like a stab in Shiro’s heart.

“Don't touch him, you bastard!”, Lance’s voice reached them. 

Following behind him were Hunk, Pidge and Matt, all bearing their weapons. They stood by Shiro’s side, taking attack stances and prepared to take action in response to any move from Kuro. 

Kuro had spied on them as well, during their sparring practice. He knew what they were capable of and how to best counter their fighting styles. He also knew that the siblings were the ones behind the improvements of the castle defenses.

"Deactivate the barrier....", Kuro demanded. His hand moved to wrap around Keith's throat, his fingertips digging into his flesh, causing the omega to let out a strangled whimper, "... or I snap his neck. "

 

There's no doubt that they were willing to comply for the sake of Keith's safety, which was their priority in that moment, even if it meant giving Kuro the opportunity to escape. 

Pidge glanced at Shiro, who tried to remain calm, but the worry for his lover was written all over his face. Shiro nodded his head. Pidge lifted the arm where she wore the bracelet that allowed her to control the castle defenses. With just a touch of her finger on one of the symbols engraved on the bracelet, the barrier was lifted.

"We did what you wanted, now take your hands off of him."

Kuro face split into a wide grin. They had no idea Kuro had left a few 'little presents' when he was still inside the castle.  

A loud sound. 

They turned their heads to the source of it and were taken aback by what they were seeing. 

An explosion from inside the castle tore a huge hole on the wall of one of the towers. Pieces of it floated in the water and fell down into the sand. And then a second explosion, whose impact was more intense, causing the tower to collapse. 

Shiro protected himself as stone debris fell upon him and the others. He, luckily, managed to avoid a giant stone pillar that came crushing down on him. 

Panic took over Shiro as he realized that the explosion redirected their attention from Kuro. He turned around. 

Kuro was gone.

And so was Keith.

The bombs placed in the castle had, conveniently, been used as a brief distraction at that moment. While their focus had turned to the explosion and the destruction it caused, his twin had escaped from them and taken his mate with him.

**Notes for the Chapter:**

> [if you liked this, please leave a comment, I will appreciate any feedback]
> 
> Sorry for taking so long to update. This was not how I first intended for the story to go and since I had to change it, I needed some time to think how this chapter would go.  
> And like I said in the beginning, magic is involved so those bombs Kuro left in the castle were crafted by Haggar and there weren't any wires or timer on it. They simply blew up.

**Author's Note:**

> I wrote this while waiting for someone to upload season 3 online. Since people seemed interested in a follow up I will proceed to update more chapters.
> 
> Please follow me on my twitter page: twitter.com/witchy_writes_s


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